164 NEWTON S PKINCIPIA. 



which had long been suspected but not proved. Pascal 

 first extended the Torricellian experiment to all the perfec 

 tion, indeed, which it has ever attained, by showing the con 

 nexion between the height of places on the earth s surface, 

 and that of the mercurial column; thus demonstrating 

 satisfactorily the pressure of the atmospherical column. 

 Torricelli had also, from experiments on the spouting of 

 water, inferred that the velocity of the spouting column, 

 or jet, is as the square root of the height of the reservoir 

 of fluid whose pressure causes the flow. So that the fun 

 damental principles being ascertained, considerable progress 

 was also made in their systematic application, when Sir 

 Isaac Newton came to treat the subject as a branch of his 

 general dynamical theory, and to investigate the laws of 

 fluids by means of those profound principles which he had 

 established with respect to all motion. Thus more was 

 done before his time, and less consequently left for him to 

 do here, than in the other branches of the general subject. 

 Secondly. It is also true that the work which he pro 

 duced upon this branch of science, did not attain the same 

 perfection under his hands, as the rest of the Principia, 

 Although he treated it upon mathematical principles, he 

 left considerably more to be done by his successors than he 

 left to be added by those who should follow him in the 

 field of Physical Astronomy. A great step was almost 

 immediately made by J. Bernouilli, in ascertaining the 

 effects of the air s resistance upon the motion of projectiles; 

 and an error so apparent was pointed out in one of the 

 Propositions in the Principia (Book II. Prop. 37*), that 

 the correction coming to the author s knowledge, he struck 

 it out of the second edition, then in the press. His ori 

 ginal solution of the problem as to spouting columns, 



* First Edition, published in 1687. 



